The most important thing I found using PLLs is basically how fast can something relieably lock in, and hold, while allowing a wide lock in range.
This really all has to do with the Low pass filter and the VCO ability.
I was going to use this with a series LC type induction heater setup but have since found they are very inefficient and have no more need for the PLL so I really haven't worked more on it.
What I did do though is try to find the root cause of why the 4046 has such a low lock in range by making simulations using the edge triggered phase detector using CMOS D flip flops, some logic, and a half bridge.
I found that the 555 use as a VCO was very limited, but I had some XR2209 VCO laying around and found they had a 1:1000 Hz sweep range so, here is what I have so far.
Keep in mind that the XR2209 operates better with a + and - voltage input, and that it actually has a negative voltage feedback to frequency with the VCO instead of a positive voltage feedback to frequency. If you want a positive feedback, you have to change the logic, I have prototyped this and it works good.
BTW. some notes:
the AND gate is on the reset of both those DFF.
The logic input and output is from +/- 10V (there are logic grounds and normal grounds in B2 spice that look the same)
The filter and voltage sources for the charge pump all have normal grounds
The Black Box/triangle 2 terminal parts represent xspice square/triangle wave VCOs that can be internally changed for all variables
I have this setup to do a FM input square wave for a simulated frequency sweep that the PLL follows..
The NAND logic on the charge pump can be substituted with an AND gate and then use another Nch mosfet with a resistor on the drain to drive the Pch mosfet at the top.
1 DFF, 1 AND, 2 Nch, 3 resistors, 1 capacitor, 1 Pch, 1 VCO, 1 Input frequency
If you want to multiple the frequency, a divider can be put between the VCO and the DFF but the VCO has to be setup for the higher frequency.
So If your simulators don't have edge triggered Phase Detectors (4046 type, type 2 PD, or type 2 PLL), there you go..
Hope that helps